An ultrasonic wave (ultrasound) is a mechanic wave generated by a piezoelectric crystal under an effect of an electric field. A sonic wave having a frequency over 20 kHz is regarded as an ultrasound. The ultrasound prevails in applications of examination, measurement and control purposes. For example, the ultrasound is applied for thickness measurement, distance measurement, medical treatments, medical diagnosis and ultrasound imaging (ultrasonography). Alternatively, by processing a material with the ultrasound, certain physical, chemical or biological properties or statuses of the material may be accelerated or changed.
An ultrasound imaging system is extensively implemented for biomedical detections. In ultrasonography, imaging is mainly achieved by pulse-echo. A principle of ultrasonography is summarized as below. A short pulse is transmitted by each array element of a transmitter. With beamforming, a time delay and a gain size of the pulses of each channel are adjusted to focus all the array signals at a position of a fixed depth on a scan line.
However, at signal transmission paths, RC delay errors resulted by hardware elements or at paths of printed circuit boards frequently demote beamforming effects from expected values. For example, complications such as lower side-lobe energy prior and subsequent to a focal point are incurred if the focal point has an excessively large radius, in a way that quality of an image converted from echo signals at a receiver is degraded.